Author + information
- Farrell O. Mendelsohn, MD∗ ()
- ↵∗Interventional Hypertension Therapies Program, Cardiology PC, 801 Princeton Avenue, SW, Suite 707, Birmingham, Alabama 35211
In the October issue of JACC: Cardiovascular Interventions, Id et al. (1) compared the results of renal denervation using the Symplicity catheter system (Medtronic, Mountain View, California) in patients with and without accessory renal arteries. This issue is not insignificant considering that 27% of the resistant hypertension population may have accessory renal arteries. These patients have, for the most part, been excluded from clinical trials of renal denervation devices. The drop in office-based systolic blood pressure at 6 months was significantly less in the patients with accessory renal arteries than in those with only main renal artery trunks (–6.2 mm Hg vs. –16.6 mm Hg). The patients with accessory renal arteries were further subdivided into 2 groups; the subgroup with complete accessory renal artery denervation experienced a slightly greater drop in systolic blood pressure than did patients with incomplete treatment of their accessory arteries (–8.8 mm Hg vs. –4.1 mm Hg).
Renal denervation targets the sympathetic nerves located in the adventitia of the renal artery wall (2). The nerves travel from the spinal cord along the artery and then to the kidney where extensive branching occurs. Early anatomic studies using electron microscopic autoradiography demonstrated that the majority of renal nerves terminate at vascular structures within the kidney (3). Based on these anatomic findings, the nerve traffic to and from the kidney corresponds at least roughly to the blood supply, traveling with both accessory and main renal arteries. So patients with accessory renal arteries may be predisposed to a lack of blood pressure response if treated with a denervation technique targeting nerves only in the main renal artery—just as was reported in the article by Id et al. (1).
Yet, why was the blood pressure-lowering response in the subgroup with “complete” renal denervation of accessory renal arteries less than that in the group with only main renal artery trunks? This difference may in part be explained by limitations of the monopolar renal denervation system used for ablation of accessory renal arteries. Cooling of monopolar catheters from blood flow is critical to avoid tissue damage from catheter overheating. In low flow conditions such as with accessory renal arteries, cooling may be inadequate. The system generator will then terminate energy delivery to prevent overheating, but it also halts the ablation, potentially compromising denervation efficacy. Other renal denervation systems that do not require cooling may be more effective for accessary renal arteries (4). It will be critical to understand the differences in renal denervation technologies and their applicability to the subset of patients with accessory renal artery anatomy.
Please note: Dr. Mendelsohn has received consulting fees from Medtronic and Boston Scientific/Vessix and has served on the medical advisory board of Boston Scientific.
- American College of Cardiology Foundation
- Id D.,
- Kaltenbach B.,
- Bertog S.C.,
- et al.
- Barajas L.,
- Powers K.
- ↵Sievert H. REDUCE-HTN clinical study interim 6- and 12-month data. Paper presented at: Transcatheter Cardiovascular Therapeutics Conference 2013; October 28, 2013; San Francisco, California.